First Stellar Abundances in the Dwarf Irregular Galaxy IC 1613

Abstract

Chemical abundances in three M supergiants in the Local Group dwarfirregular galaxy IC 1613 have been determined using high-resolutionspectra obtained with the UVES spectrograph on the ESO 8.2 m Kueyentelescope. A detailed synthetic-spectrum analysis has been used todetermine the atmospheric parameters and abundances of O, Na, Mg, Al,Si, Ca, Sc, Ti, Cr, Fe, Co, Ni, La, and Eu. We find the overallmetallicity of the stars to be [Fe/H] = -0.67 {\plusmn} 0.09 and the age9-13 Myr, which is in excellent agreement with the present-day values inthe age-metallicity relationship model of IC 1613 by Skillman et al. Wehave found that the three supergiants investigated have a mean[{α}/Fe] equal to about -0.1, which is lower than seen in Galacticstars at the same metallicity and is in agreement with the resultsobtained in other dwarf irregular galaxies. The oxygen abundances are inagreement with the upper values of the nebular oxygen determinations inIC 1613. The abundance ratios of s- and r-process elements to iron areenhanced relative to solar by about 0.3 dex. The abundance pattern ofthe elements studied is similar to that of the Small Magellanic Cloud,except for Co and Ni, which are underabundant in the SMC. The observedelemental abundances are generally in very good agreement with therecent chemical evolution model of Yuk and Lee.Based on observations collected with the Very Large Telescope and the2.2 m Telescope of the European Southern Observatory within theObserving Programs 70.B-0361(A) and 072.D-0113(D).